Process for cross-linking cellulose with formaldehyde adducts of divinyl sulfone



United States Patent PRGCESS FOR (IROSS-LHNKING CELLUiL-QSE WETH FORIvEALDEHYDE ADDUCTS 6F DWINYL filJLFQNE Clark M. Weich, New @rleans, La,assignor to the United States of America as represented by the Secretaryof Agriculture No Drawing. (lriginal application 32m. 23, 1962, Ser. No.168,288. Divided and this application July 15, 1963, Ser. No. 315,432

6 Claims. (Cl. 2fi0-697) (Granted under Title 35, US. Code (1952), see.266) A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

. This application is a division of Serial No. 168,288, filed January23, 1962.

This invention relates to the preparation of novel addition products ofdivinyl sulfone with formaldehyde, and the application of such productsto cellulose to produce novel crosslinked and partially etherifiedcelluloses. An object of the invention is to prepare cellulosicmaterials, particularly cellulosic textiles, having durable wrinkleresistance and increased resistance to shrinkage and stretching. Asecond object is to provide a method of treating cellulosic textiles inwhich method the odor and inhalation toxicity problems associated withthe use of free divinyl sulfone are eliminated. Other objects will beapparent from the description which follows.

It is well known that formaldehyde in aqueous solution exists as aseries of hydrates of the structure HO(CH O) H Where n is in the rangel3 for most of the solute (I. F. Walker, Formaldehyde, ReinholdPublishing Corporation, 1953, pp. 47-55). In the hydrate form,formaldehyde is a weak acid and reacts with alkalies to form salts(Walker, p. 1789) which may serve as intermediates in a number ofreactions. In the present invention it is shown that excess aqueousformaldehyde reacts with divinyl sulfone in the presence of alkalinecatalysts, denoted by X, in the following manner:

Highly water-soluble adducts are formed when the mole ratio offormaldehyde/divinyl sulfone used is in the range 0.9 to 10.0. When themole ratio is in the range 0.2 to 0.9, the following reaction occurs:

In the above equations, 11 has a value of 1-3, as shown by Walker, citedabove.

The adducts formed in this reaction are but slightly soluble in water.All the adducts obtained in these reactions are found to be reactivetoward cellulose and are useful in introducing crosslinks. Solutions ofthe watersoluble types of adducts may be freed of any divinyl sulfoneodor by extraction of traces of unreacted divinyl sulfone with awater-immiscible inert solvent such as benzene. The sparinglyWater-soluble type of adduct may be freed of divinyl sulfone odor byextraction of any unreacted divinyl sulfone with Water.

3,219,7d8 Patented Nov. 23, 1965 Catalysts suitable for preparation ofthese adducts are soluble bases such as alkali metal hydroxides andcarbonates, alkaline earth metal hydroxides, organic quaternary ammoniumhydroxides and carbonates, and tertiary aliphatic amines. Basesconsiderably stronger than alkali metal carbonates have thedisadvantage, however, of accelerating even at moderate temperatures thereaction of divinyl sulfone with water which may be present, thusdecreasing the yield of the formaldehyde-divinyl sulfone adducts.

The reaction of formaldehyde and divinyl sulfone is advantageouslycarried out in solution and preferably in aqueous solution, usingcatalyst concentrations below 5%, and temperatures of 20100 C. The rateof reaction will vary with the particular catalyst present and itsconcentration, as well as the concentrations of formaldehyde and divinylsulfone. At low catalyst concentrations, warming is required to initiatethe reaction. However, the reaction is exothermic once it is initiated,and proceeds quite rapidly at temperatures below those required forreaction of divinyl sulfone with water.

The application of the highly water-soluble type of adduct to celluloseis simple and rapid. The solution 0btained in preparing the adduct isdiluted to the strength desired, an alkaline catalyst is added if thatalready present is too dilute, and the solution is applied to cellulosein the form of fiber, yarn, or fabric. The cellulose is then kept for05-30 minutes at temperatures ranging from 20-l70 C., the optimumtemperature depending upon the type and concentration of catalyst used.Catalysts suitable for the application of the adducts to cellulose arealkali metal hydroxides, carbonates and bicarbonates, alkaline earthmetal hydroxides and organic quaternary ammonium hydroxides, carbonatesand bicarbonates. Although catalyst concentrations of 0.l30% may beused, concentrations of 13% are preferred when outing at l20l60 C., andunder these conditions, curing is complete in 0.5-5 minutes.

The application to cellulose of the sparingly watersoluble type ofadduct described above may be carried out by dissolving the adduct in aninert water-miscible volatile organic solvent and diluting the latterwith water to the desired concentration, followed by addition ofcatalyst and curing as with the highly Water-soluble types of adducts.

A further variation in the process of this invention is the applicationto cellulose of a mixture of divinyl sulfone, formaldehyde, and analkaline catalyst in an inert volatile solvent such as Water, followedby curing in the manner described for the preformed adducts. Thecatalyst concentration is kept at or below 3% so that the formaldehydeand divinyl sulfone do not react at room temperature. The catalystssuitable for this method are the same as those used in applying thepreformed adducts to cellulose. While this variation has thedisadvantage that the treating solution retains the irritating andlachrymatory odor of divinyl sulfone, it resembles the other methods ingiving a higher etliciency of reaction with cellulose than is obtainedin the absence of the formaldehyde.

The formation of crosslinks in cellulose materials treated by theprocesses of this invention is evidenced not only by enhanced wrinkleresistance and other forms of dimensional stability, but also byinsolubility of the treated fibers in cuprammonium hydroxide orcupriethylenediamine solution. While it is believed that the adducts,particularly those of the sparingly Water-soluble type, are capable ofacting directly as crosslinking agents, it is also possible that theadducts undergo partial dissociation under the curing conditions used,to generate appreciable amounts of divinyl sulfone in situ. This sulfonealso is a highly effective crosslinking agent.

An unexpected feature of cellulose fabrics treated by the processes ofthis invention is the fact that both their tensile strength and theirwrinkle resistance in the wet state can be further increased bysubsequent mercerization with aqueous sodium hydroxide or potassiumhydroxide at concentrations of 17-35%. The great durability of thefinishes described herein is also demonstrated by the fact that theywithstand treatment with such strong alkalies.

The following examples illustrate the preparation and application tocellulose of adducts formed by divinyl sulfone with formaldehyde atvarying mole ratios of the two reactants. Crease recovery angles citedare double the values measured in the warp direction by the Monsantocrease recovery test. The adaptation of Lawrence and Phillips, Am.Dyestuff Reptr., 45, p. 548 (1956) was used for crease recovery tests inthe wet state. A Scott tester was used for warp breaking strengthdeterminations. The fabric used was desized, scoured and bleached 80 x80 cotton print cloth.

Example 1 A solution of formaldehyde-divinyl sulfone adduct (highlysoluble type) was prepared as follows: to ml. (0.1 mole) of divinylsulfone in 25 ml. of water was added ml. of 40% aqueous formaldehyde(0.2 mole) and 1.0 g. of sodium carbonate monohydrate. The mixture waswarmed to 40 C. with stirring. A mildly exothermic reaction began andthe temperature gradually rose to 50 C. even though heating had beenremoved. After 15 minutes longer, the temperature began to fall. Themixture was kept at 50 for 15 minutes more and then allowed to stand forone hour. It was shaken with three ml. portions of benzene to removetraces of divinyl sulfone. There was obtained 44 ml. of adduct solutionhaving a concentration of about In a control experiment in which 10 ml.of divinyl sulfone was heated with 40 ml. of water and 1 g. of sodiumcarbonate monohydrate in the absence of formaldehyde, no reactionoccurred until the temperature was raised to 90, whereupon an insolublepolymer separated. This shows that the reaction of divinyl sulfone withformaldehyde leads to a different adduct than does the reaction ofdivinyl sulfone with water.

Example 2 The adduct solution of Example 1 was applied to print cloth inthe following way: the solution, which already contained sufficientsodium carbonate to serve as a catalyst, was applied in one dip and onenip to the fabric, the pressure of the wringer rolls being adjusted togive a wet pickup of 125%. The fabric was oven-cured at a specifiedtemperature for 5 minutes. It was washed thoroughly in both cold and hotwater, heat-dried and air equilibrated to constant moisture content.Samples of the treated fabric were subsequently mercerized by beingsoaked in 20% sodium hydroxide for 5 minutes, after which they wereagain washed, dried and equilibrated. The properties of the treatedfabrics were as follows:

B Compared at constant thread count.

4 Example 3 The adduct preparation of Example 1 was repeated using 10ml. (0.1 mole) of divinyl sulfone, 7.6 ml. (0.1 mole) of 40%formaldehyde, 30 ml. of water and 1.00 g. of sodium carbonatemonohydrate. The exothermic reaction was carried out at 40-55 C. asbefore. After the usual benzene extractions, there was obtained 43 ml.of a solution containing about 25% by weight of adduct.

Example 4 The adduct solution of Example 3 was diluted with threevolumes of water, and based on the total solution, 1.85% by Weight ofsodium bicarbonate was added. The solution was applied to print cloth inone clip and one nip to a wet picket of 113%. The fabric was ovencuredat 135 C. for 5 minutes. It was washed, heatdried and air-equilibrated.The treated cloth showed a gain in weight of 5%, a sulfur content of0.80%, a crease recovery angle of 283 wet and 255 dry, and a breakingstrength loss of 45%. Untreated fabric showed crease recovery angles of160 wet and 157 dry.

Example 5 The adduct preparation of Example 1 was repeate'd using 10 ml.(0.1 mole) of divinyl sulfone, 5.7 ml. (0.075 mole) of 40% formaldehyde,30 ml. of water and 1.00 g. of sodium carbonate monohydrate. Theexothermic reaction was carried out at 4555 C., as before. The reactionmixture was shaken with 20 ml. of benzene, causing three liquid layersto form. The two denser layers were added to 30 ml. of water and 0.35ml. of glacial acetic acid, bringing the pH to 8. Then 1.35 g. of sodiumbicarbonate and 20 ml. of tetrahydrofuran were added, giving ml. of ahomogeneous solution containing the adduct in a concentration of about15%.

Evaporation of the benzene extract gave only 0.3 g. of divinyl sulfone,showing practically all of the divinyl sulfone had reacted withformaldehyde.

Example 6 The adduct solution of Example 5 was diluted to a specifiedstrength, and a specified amount of extra sodium bicarbonate was addedto compensate for dilution of catalyst already present. The solution wasthen applied to print cloth in one dip and one nip to a wet pickup of113118%, and the cloth was cured at C. for 5 min utes. The cloth wassubsequently washed, oven-dried, and air-equilibrated. The fabricproperties were as follows:

Crease re- Adduet Con- Extra Weight Percent eovery, deg. Strength Icentration, NaHCO gain, sulfur loss, perpereent percent percent cent WetDry 15 0.0 8. 4 1. 34 269 231 36 7.5 1. 0 5. 2 0. 83 250 242 37Untreated fabric 157 O a Compared at constant thread count.

Example 7 To the adduct solution of Example 7 was added 8% by volume oftetrahydrofuran and 1% by weight of sodium carbonate. The solution Wasapplied to print cloth in one dip and one nip to a Wet pickup of 112%,and the cloth was cured at 135 C. for 5 minutes. The cloth wassubsequently washed, oven-dried and airequilibrated. The fabricproperties were as follows: weight gain-8%, sulfur content-1.21%, wetcrease recovery278, dry crease recovery-241, breaking strength loss40%.Untreated fabric showed crease recovery angles of 160 wet and 157 dry.

Example 9 Print cloth was soaked in a solution containing 5 ml. (0.06mole) of 36% aqueous formaldehyde, 2.0 ml. (0.02 mole) of divinylsulfone and 0.25 g. of sodium carbonate in 15 ml. of water at roomtemperature. The fabric was then oven-cured at 135 C. for 10 minutes,and was subsequently washed, dried and air-equilibrated. It showed aWeight increase of 10% and had high Wrinkle resistance in both the wetand dry states.

The same experiment carried out in the absence of formaldehyde gavefabric having a weight increase of 6%. The experiment conducted withformaldehyde present but divinyl sulfone absent gave a weight increaseof only 0.9%.

I claim:

1. A process for preparing addition products of formaldehyde withdivinyl sulfone which comprises reacting formaldehyde with divinylsulfone in the presence of water at 20100 C. in an inert solvent in thepresence of an alkaline catalyst, the mole ratio of formaldehyde todivinyl sulfone being about from 0.2/1 to 10.0/ 1.

2. The process of claim 1 wherein the mole ratio of formaldehyde todivinyl sulfone is from 0.9 to 10.0 and the product so produced ishighly water soluble.

3. The process of claim 1 wherein the mole ratio of formaldehyde todivinyl sulfone is greater than 0.2 but less than 0.9, and the productso produced is relatively water-insoluble.

4. An adduct of divinyl sulfone and formaldehyde from the groupconsisting of 5. A highly Water soluble adduct of divinyl sulfone andformaldehyde having the formula:

where n is an integer from 13.

6. A slightly water soluble adduct of divinyl sulfone and formaldehydehaving the formula:

Where n is an integer from 13.

References Cited by the Examiner UNITED STATES PATENTS 2,505,366 4/ 1950Schoene. 2,878,294 3/1959 Kress 81 16 3,068,123 12/ 1962 Feldmann.

OTHER REFERENCES Welch et al.: Textile Research Journal, vol. 31, pp.84-86 (1961).

NORMAN G. TORCHIN, Primary Examiner,

1. A PROCESS FOR PREPARING ADDITION PRODUCTION OF FORMALDEHYDE WITHDIVINYL SULFONE WHICH COMPRISES REACTING FORMALDEHYDE WITH DIVINYLSULFONE IN THE PRESENCE OF WATER AT 20-100*C. IN AN INERT SOLVENT IN THEPRESENCE OF AN LAKALINE CATALYST, THE MOLE RATIO OF FORMALDEHYDE TODIVINYL SULFONE BEING ABOUT FROM 0.2/1 TO 10.0/1.